The role of sequestering agents in softening water by complexing the "hardness" cations in water supplies is well-known. Sequestering agents are recognized aids in detergent processes because they form a soluble complex with calcium and magnesium ions which can react with soaps and other anionic surfactants and otherwise adversely affect detergency.
Polyphosphates such as tripolyphosphates and pyrophosphates are widely used as ingredients in detergent compositions in part because of their property of sequestering hardness ions. Such phosphorus-containing compounds as well as nitrogen-containing compounds, e.g., nitrilotriacetates, are highly effective. However, the effect of the phosphorus content and the nitrogen content of these sequestering agents upon eutrophication of lakes and streams has been questioned and the use of phosphates in detergent compositions has been subject to government scrutiny, regulation or prohibition.
These circumstances have developed a need for highly effective and efficient phosphorus-free and nitrogen-free sequestering agents and detergency builders.
U.S. Pat. No. 3,692,685, describes detergent compositions containing an ether polycarboxylate having the structure: ##STR2##
In the above structure of U.S. Pat. No. 3,692,685, R is H or --CH.sub.2 COONa.
U.S. Pat. No. 4,228,300, describes ether polycarboxylate sequestering agents and detergency builders having the structure: ##STR3##
In the above structure of U.S. Pat. No. 4,228,300, M is alkali metal or ammonium, R.sub.1 and R.sub.2 are hydrogen, methyl or ethyl and R.sub.3 is hydrogen, methyl, ethyl or COOM.
U.S. Pat. No. 3,769,223, describes 1-oxacyclopropane-2,3-dicarboxylic acid (i.e., epoxysuccinic acid) and its soluble salts as detergent builders.
U.S. Pat. No. 3,776,850, describes polymers to be used as detergent builders which have the structure: ##STR4##
In the above structure of U.S. Pat. No. 3,776,850, R is hydrogen or other specified radicals and n is from 2 to about 40, preferably from 2 to about 6. The polymers are prepared by polymerization of the diethyl ester of 1-oxacyclopropane-2,3-dicarboxylic acid (i.e., epoxysuccinic acid) in the presence of a boron trifluoride catalyst followed by saponification. Detergent compositions are exemplified in which n is said to have an average value of approximately 3 or 4. In fact, the disclosed synthesis method yields mixtures of materials which contain very low levels of the n=3 and n=4 components.
U.S. Pat. No. 4,654,159 describes the use of polyepoxy succinic acid as a sequestering agent in detergent compositions.